This invention relates to crosslinkable polyester resin compositions which are capable of setting to form a hard mass and which are suitable for use with anchoring or reinforcing elements employed in mining and other operations. The invention also provides a system for providing anchoring or structural support in mining and other operations.
It has been the practice to provide roof and wall control in mines with reinforcing elements. These are usually installed by drilling a hole in the roof or other surface and inserting into the hole a settable material and then inserting a reinforcing element, referred to as a bar or rebar. The settable material is allowed to form a hard mass around the reinforcing element. The settable material often comprises a liquid polyester resin. Usually this is mixed with aggregate and enclosed within a tube of frangible material such as paper, glass or plastic. A fluid catalyst component is also provided. Insertion of the reinforcing element causes mixing of the ingredients and initiates the curing reaction which causes the resin to form a hard mass around the reinforcing element.
There have been proposals to employ compositions which can be cured by heat generated by the action of rotating the reinforcing element in the composition. For example, U.K.Patent No 2,007,741A describes a process for positioning a strengthening rod in mine levels in which there is introduced into a long bore made in a wall to be strengthened a thermosetting resin composition and a metal rod of substantially the same length as the bore and the rod is rotated at a speed which causes it to heat up to the hardening temperature of the composition so as to cause the rod to be sealed in the bore by the hardened composition. The resinous compositions are either liquid or semiliquid which can be injected into the borehole or are packaged in a plastic sheath. A later proposal, U.K. Patent No 2,063,888A describes a similar process and liquid resinous composition which comprises as filler, carbon black and defined amounts of chalk and quartz. The carbon black is said to facilitate achieving a better compromise between the reactivity and viscosity of the composition.
The compositions used in the cartridges described in these patent applications and those which are now widely used are either liquid or semi-liquid and need to be contained in a frangible tube in order to retain their shape which is usually that of a long thin and flexible cylinder.
The present invention provides a solution to this problem by the provision of a crosslinkable polyester resin composition which is solid at 20xc2x0 C. but which is permits insertion of a reinforcing element and rotation thereof to cause mixing of the composition with a catalyst.
According to the present invention there is provided a solid cross linkable composition suitable for use with a reinforcing element for reinforcing rock and other structures, said composition comprising:
(a) from about 10 to 45% of a crosslinkable unsaturated polyester resin,
(b) from about 40 to 90% of a filler and
c) from about 1 to 15% of an ethylenically unsaturated monomer copolymerisable with the unsaturated polyester, the percentages being by weight based on the total weight of (a), (b) and (c), the composition being solid but permitting insertion and rotation of a reinforcing element to cause mixing of the composition with a crosslinking catalyst which effects curing of the resin to form a hard mass.
The compositions of the present invention are suitable for use in providing structural support such as reinforcement or providing an anchoring means eg starter bars in concrete, fixings in walls, machinery anchors and the like.
Because the compositions of the invention are solid at 20xc2x0 C. they can be shaped and will retain their shape without the need for the frangible tube used in the prior art. Preferably the compositions are solid ie retain their shape at temperatures up to 40xc2x0 C.
The hardness of the solid composition permits the insertion of a reinforcing element and rotation of the reinforcing element which causes mixing of the resin and catalyst. The resin composition and copolymerisable monomer are sufficiently reactive that mixing the crosslinking catalyst with the composition under ambient conditions eg 20xc2x0 C. will effect the crosslinking of the resin ie the resin is cold cured without the application of heat, although a small amount of heat may be generated by the rotation of the reinforcing element.